Copies: Lisa Kellogg Janis Lutrick Mala Pattanayek Wini Curley Adrienne LaPierre Kim Walsh

Transcription

1 MEMO T: Yvnne Meeks/PG&E Cpies: Lisa Kellgg Janis Lutrick Mala Pattanayek Wini Curley Adrienne LaPierre Kim Walsh ARCADIS U.S., Inc. 100 Mntgmery Street Suite 300 San Francisc Califrnia Tel Fax Frm: The ARCADIS Risk Assessment Team Date: January 28, 2013 ARCADIS Prject N.: RC Subject: Final RAWP Addendum 2 - Scpe The purpse f this memrandum is t briefly list the additinal infrmatin required t cmplete the wrk plan fr the frthcming sil risk assessment at the Tpck Cmpressr Statin, Needles, Califrnia. The wrk plan currently cnsists f the fllwing dcuments: Technical Memrandum: Tpck Cmpressr Statin Eclgical Cnceptual Site Mdels, Assessment Endpints, and Receptrs f Cncern (ARCADIS BBL, 2007a) Technical Memrandum: Tpck Cmpressr Statin Eclgical Expsure Parameters, Biaccumulatin Factrs, and Txicity Reference Values (ARCADIS BBL, 2007b) Risk Assessment Wrk Plan (RAWP; ARCADIS, 2008) RAWP Addendum (ARCADIS, 2009a). The additinal infrmatin required t cmplete the risk assessment will be prvided in RAWP Addendum 2 and will cnsist f bth human health risk assessment (HHRA) and eclgical risk assessment (ERA) tpics as listed belw. 1/6

2 Human Health Risk Assessment New Tpics In accrdance with the Sil RCRA Facility Investigatin/Remedial Investigatin (RFI/RI) Wrk Plan Respnse t Cmment (RTC) 74(e), Pacific Gas & Electric (PG&E), U.S. Department f the Interir (DOI), Department f Txic Substances Cntrl (DTSC), and stakehlders will wrk thrugh a prcess f data presentatin and interpretatin. RAWP Addendum 2 will include a descriptin f this prcess. The prcess will include at least ne example f cmputing expsure pint cncentratins frm a data set, and may include wrking grups, demnstratins, and technical memranda. In respnse t specific agency directin resulting frm stakehlder cmments, present the results f a literature search, currently being cnducted in rder t understand the ptential fr hexavalent and/r trivalent chrmium t be taken up int plant tissue. The literature search will fcus n arrwweed, but will summarize ur findings frm ther plant species as well. The literature search will include a discussin f Califrnia Envirnmental Prtectin Agency s (CalEPA s) mst recent relevant guidance. The results f the literature search will assist in the develpment f an apprpriate methd fr evaluating (e.g., quantitative r qualitative) the ptential fr uptake f hexavalent chrmium and/r trivalent chrmium int plant tissue and resulting human r envirnmental impacts. In respnse t agency directin resulting frm stakehlder cmments, revise CSMs: Include cntact with plants (e.g., arrwweed) fr tribal user fr quantitative r qualitative evaluatin. Specific pathways will be identified based n the literature search and in crdinatin with the tribes. Include sediment and prewater cntact as cmplete if apprpriate based n data frm Sil RFI/RI (Vlume 3). In respnse t agency directin resulting frm stakehlder cmments and based n the results f the literature search, add recmmendatins fr addressing ptential expsure t arrwweed (and/r ther relevant plants) in the quantitative HHRA tribal user scenari. Recmmendatins fr intake assumptins will be develped wrking with the tribes (assuming, that is, that all agree that this expsure pathway shuld be quantified). In respnse t agency directin resulting frm stakehlder cmments, incrprate recmmended tribal use expsure assumptins frm March 14, 2012, mem frm Mike Sullivan and Eric Rsenblum n behalf f the Tribes t DTSC/DOI. 2/6

3 In respnse t agency directin resulting frm stakehlder cmments, frmalize that cmmercial/industrial sil screening levels (Califrnia Human Health Screening Levels [CHHSLs] r U.S. Envirnmental Prtectin Agency [USEPA] Reginal Screening Levels [RSLs]) will initially be used t screen sediment data fr human cntact. If the cncentratins f chemicals in sediment exceed the cmmercial/industrial CHHSL fr sil, then further evaluatin can be cnsidered such as develping a site-specific sediment screening level prtective f recreatrs and tribal users. Surface water criteria will be used t screen prewater data fr human cntact. The addendum will include develpment f sediment screening cncentratins fr hexavalent chrmium prtective f relevant eclgical ppulatins. In accrdance with standard risk assessment practice, revise descriptins f existing expsure areas, as applicable, t specifically include East Ravine sil in apprpriate categry (Bat Cave Wash [BCW] r all ther utside the fence areas r a unique area). In accrdance with standard risk assessment practice, revise apprach t risk assessment fr the cmmercial/industrial wrker inside the fence line (frmerly Part B) t reflect the anticipated limitatins fr the planned available sil data. Further Develpment f Existing Infrmatin in the RAWP In respnse t agency directin, additinal infrmatin is needed fr specific sil expsure assumptins fr three ptential human receptrs: Adult and Yuth Recreatinal User Develp sil expsure assumptins fr bth spradic and shrtterm uses in crdinatin with the agencies. Maintenance Wrker Develp specific sil expsure assumptins with input frm PG&E n typical use patterns. Future Hypthetical Residential User Wrk with DOI t gain cncurrence n the apprach fr addressing DOI scenari fr cntact with vegetables, fruits, and pultry and their uptake frm sil. Eclgical Risk Assessment Add desert bighrn sheep t the list f representative receptrs in anticipatin f request frm DTSC t be cnsistent with the Final Grundwater Human Health and Eclgical Risk Assessment (GWRA; ARCADIS 2009b) scpe and bservatins by PG&E emplyees at Tpck Cmpressr Statin. Include receptr selectin criteria. 3/6

4 Specify the expsure parameters and expsure areas. The existing expsure areas fr large hme range receptrs were established withut cnsideratin f direct bservatins f the sheep by Curt Russell r thers at Tpck Cmpressr Statin, and withut regard t elevatin which may affect the distributin f the sheep. PG&E will wrk with the agencies t develp apprpriate expsure scenaris fr the bighrn sheep. The expsure area fr the bighrn sheep will then be established in the RAWP Addendum 2 with cnsideratin f the large hme range f the sheep, direct incidental bservatins f the sheep near the Tpck Cmpressr Statin, and available habitat. Revise Figures 3-1, 1, and 2 frm the RAWP Addendum (shwing sampling and expsure depth intervals) t include large herbivrus mammals represented by the desert bighrn sheep. Specify plant rting depth and crrespnding expsure interval assumptin fr plant tissue cncentratins fr the sheep mdel. Remve allmetric cnversin frm txicity reference values (TRVs; prpsed and Bilgical Technical Assistance Grup [BTAG]) cnsistent with DTSC Eclgical Risk Assessment Sectin (ERAS) cmments dated June 22, Describe apprach t amending the Final GWRA (including Appendix I; ARCADIS 2009b) t include grundwater data cllected frm the East Ravine after the GWRA was cmpleted. Describe apprach t updating grundwater-t-surface water pathway analysis t reflect new grundwater and prewater data, as apprpriate. RAWP Addendum 2 will include specific water quality cmparisn values that will be used t interpret prewater data. Describe apprach t amending the Final GWRA (including Appendix I; ARCADIS 2009b) t include new infrmatin n phreatphytic vegetatin at AOC-10 and AOC-11. Select hexavalent chrmium eclgical cmparisn value (ECV) fr sediment. PG&E and the agencies agreed t a scientific/management decisin pint (SMDP) meeting t review the results f the sil and sediment sampling in BCW when they becme available. The sediment ECV wuld be used t interpret the sediment data. The sil backgrund value fr hexavalent chrmium was used fr cmparisn during data gaps evaluatin. Tentative Milestne Schedule Draft Mem t DOI and DTSC frm Michael Sullivan (FMIT cnsultant) and Eric Rsenblum (TRC): Develpment f Tribal-Specific Land Use Risk Assessment 03/14/12 (actual date) 4/6

5 DOI and DTSC direct PG&E and its cntractrs t cnduct a literature search t better understand the ptential fr hexavalent and ttal chrmium t be taken up int plant tissue, including arrwweed 05/02/12 (actual date) Results f Plant Uptake Literature Search and Mapping 07/15/12 Draft Technical Memrandum: The Ptential fr Chrmium Uptake by Arrwweed and Ptential Expsure Pathways (Arrweed Mem) Mid-Nvember 2012 Final Arrwweed Mem t Stakehlders End February 2013 Scping Meeting(s) February thrugh April 2013 Specific Assumptins fr Recreatinal User (preference fr directin frm DOI, the landwner) and Future Hypthetical Residential User With PG&E t identify Maintenance Wrker expsure assumptins With the tribes regarding methds/assumptins fr assessing uptake and ptential tribal user expsure t hexavalent chrmium and ttal chrmium in plants, including arrwweed Wrking grup fr sil data presentatin, interpretatin, and expsure pint calculatin Draft RAWP Addendum 2 t Stakehlders and Agencies Early September 2013 Stakehlder and Agency Input n RAWP Addendum 2 Mid Octber 2013Submit RTCs n RAWP Addendum 2 Mid Nvember 2013 Meeting t discuss RTCs n RAWP Addendum 2 Early December 2013 Stakehlder and Agency Input n RTCs t RAWP Addendum 2 Early January 2014 Finalize RAWP Addendum 2 r prvide Respnses t Stakehlder Cmments Early February 2014 Agency apprval n RAWP Addendum 2 Mid March 2014 Begin Sil Risk Assessment Beginning f August 2015 (culd start the sil risk assessment after the data analysis is cmpleted in Mid- September 2014) 5/6

6 Final Sil RFI/RI Vlume 3 Submitted Early July 2015 Agencies apprve Final Sil RFI/RI Vlume 3 Beginning f August 2015 Sil Risk Assessment Draft t Agencies End f Nvember 2015 Sil Risk Assessment Final t Agencies Beginning f April 2016 References ARCADIS BBL. 2007a. Technical Memrandum: Tpck Cmpressr Statin Eclgical Cnceptual Site Mdels, Assessment Endpints, and Receptrs f Cncern, Tpck Cmpressr Statin, Needles, Califrnia. April. ARCADIS BBL. 2007b. Technical Memrandum: Tpck Cmpressr Statin Eclgical Expsure Parameters, Biaccumulatin Factrs, and Txicity Reference Values, Tpck Cmpressr Statin, Needles, Califrnia. June. ARCADIS Human Health and Eclgical Risk Assessment Wrk Plan (RAWP), Tpck Cmpressr Statin, Needles, Califrnia. August. ARCADIS. 2009a. Revised Addendum t the Revised Human Health and Eclgical Risk Assessment Wrk Plan (August 2008), Tpck Cmpressr Statin, Needles, Califrnia. February. ARCADIS. 2009b. Final Grundwater Human Health and Eclgical Risk Assessment, Tpck Cmpressr Statin, Needles, Califrnia. December. 6/6